The present application claims priority to Japanese Application No. P11-205216 filed Jul. 19, 1999; which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a Group III nitride compound semiconductor thin film comprising a Group III element such as aluminum (Al), gallium (Ga), indium (In) or boron (B), and nitrogen (N), and a deposition method thereof. The present invention also relates to a semiconductor device comprising such a Group III nitride compound semiconductor thin film, and a manufacturing method thereof.
2. Description of the Related Art
GaN (gallium nitride), InGaN (indium gallium nitride) compound crystal, GaAlN (gallium aluminum nitride) compound crystal and InAlGaN (indium aluminum gallium nitride) compound crystal are typical Group III nitride compound semiconductors. Group III nitride compound semiconductors are attractive as practical semiconductor materials applicable to light emitting devices such as a light emitting diode (LED) that emits blue light or a laser diode (LD) that emits blue light. Active exercise of research and development thereof is still going on.
In the related art practice, a Group III nitride compound semiconductor is grown on a substrate by MOCVD (Metal Organic Chemical Vapor Deposition), which is also called MOVPE (Metal Organic Vapor Phase Epitaxy), or by MBE (Molecular Beam Epitaxy) to be formed into a single-crystal thin film.
In MOCVD, a Group III nitride compound semiconductor is obtained through chemical reactions between material gases of a Group III element and nitrogen, and is heteroepitaxially grown on a substrate. MOCVD has an advantage that a single-crystal thin film having a uniform composition can be deposited on a substrate. MOCVD also allows the substrate temperature (growth temperature) to be set high. This contributes to another advantage of relative easiness of depositing a single-crystal thin film of excellent crystalline, or a single-crystal thin film having few lattice defects such as dislocations.
On the other hand, in MBE, a substrate is irradiated with particle beams of a Group III element and nitrogen, which are evaporated from a Knudsen cell, to grow a crystal thereon. Thus, MBE has a difficulty in forming a thin film of uniform composition and film thickness. In addition, MBE requires a low substrate temperature (growth temperature) in order to suppress desorption of nitrogen flom the surface of a thin film at the time of crystal growth. This makes it difficult to form a single-crystal thin film of excellent crystalline. Since the light emission efficiency of a light emitting device is said to depend largely on the crystalline of a thin film, MOCVD, which is practically effective, is frequently used with the current state of the art.
MOCVD, however, has a problem of the limited material and size of a substrate used. That is, a substrate used in MOCVD has to have a lattice constant substantially equal to that of a Group III nitride compound semiconductor to be grown thereon. Moreover, a substrate used in MOCVD has to have high heat resistance.
Present practice followed in growing a Group III nitride compound semiconductor is to use a crystalline sapphire (xcex1-Al2O3) substrate. Sapphire of this type has a lattice constant approximately equal to those of Group III nitride compound semiconductors, especially GaN. The sapphire also has excellent heat resistance. For these reasons, the sapphire is suitable for a material of substrates used in MOCVD.
The use of sapphire substrates, however, involves the growth on c surfaces. Thus, sapphire substrates have a problem in workability or formability, resulting in high materials cost.
Another problem with sapphire substrates is low production efficiency. Since it is difficult to deposit a thin film of uniform film thickness over the entire surface of a substrate, a substrate of large surface area cannot be used (with the current state of art, the maximum size is about 8 inches).
Furthermore, a single-crystal Group III nitride compound semiconductor thin film manufactured by MOCVD includes lattice defects such as dislocations at a rate of about 1010 cmxe2x88x922. The use of such a single-crystal Group III nitride compound semiconductor thin film as a luminescent material in an LED causes an increase in non-radiative recombination probability in which electrons recombine with holes without emitting radiation, resulting in a problem of deterioration in light emission efficiency.
The present invention has been achieved to overcome the above-described problems. A first object of the invention is to provide a Group III nitride compound semiconductor thin film which can, be deposited on any given substrate and a deposition method thereof, and a semiconductor device using such a Group III nitride compound semiconductor and a manufacturing method thereof.
A second object of the invention is to provide a Group III nitride compound semiconductor thin film of uniform film quality and excellent crystalline and a deposition method thereof, and a semiconductor device using such a Group III nitride compound semiconductor and a manufacturing method thereof.
A deposition method of a Group III nitride compound semiconductor thin film according to the invention is a method for depositing a Group III nitride compound semiconductor thin film comprising at least one Group III element and nitrogen, wherein a poly-crystalline Group III nitride compound semiconductor thin film is deposited on a substrate by sputtering using a target comprised of a Group III nitride compound in a plasma atmosphere of gas comprising at least nitrogen.
Another deposition method of a Group III nitride compound semiconductor thin film according to the invention comprises steps of: depositing, on a substrate, a poly-crystalline Group III nitride compound semiconductor thin film comprising at least one Group III element and nitrogen; and removing a lattice defect which occurs in the poly-crystalline Group III nitride compound semiconductor thin film, by irradiating the poly-crystalline Group III nitride compound semiconductor thin film deposited on the substrate with a pulsed laser.
Still another deposition method of a Group III nitride compound semiconductor thin film according to the invention comprises steps of: depositing, on a substrate, a single-crystal Group III nitride compound semiconductor thin film comprising at least one Group III element and nitrogen; and removing a lattice defect which occurs in the single-crystal Group III nitride compound semiconductor thin film, by irradiating the single-crystal Group III nitride compound semiconductor thin film deposited on the substrate with a pulsed laser.
A Group III nitride compound semiconductor thin film according to the invention is a Group III nitride compound semiconductor thin film comprising at least one Group III element and nitrogen, wherein the Group III nitride compound semiconductor thin film is deposited by sputtering using a target comprised of a Group III nitride compound in a plasma atmosphere of gas comprising at least nitrogen, and has a poly-crystalline structure.
A manufacturing method of a semiconductor device according to the invention is a manufacturing method of a semiconductor device comprising a Group III nitride compound semiconductor layer comprising at least one Group III element and nitrogen, wherein a poly-crystalline Group III nitride compound semiconductor layer is deposited on a substrate by sputtering using a target comprised of a Group III nitride compound in a plasma atmosphere of gas comprising at least nitrogen.
Another manufacturing method of a semiconductor device according to the invention is a manufacturing method of a semiconductor device comprising a Group III nitride compound semiconductor layer comprising at least one Group III element and nitrogen, the method comprising steps of: depositing, on a substrate, a poly-crystalline Group III nitride compound semiconductor layer comprising at least one Group III element and nitrogen; and removing a lattice defect which occurs in the poly-crystalline Group III nitride compound semiconductor layer, by irradiating the poly-crystalline Group III nitride compound semiconductor layer deposited on the substrate with a pulsed laser.
Still another manufacturing method of a semiconductor device according to the invention is a manufacturing method of a semiconductor device comprising a Group III nitride compound semiconductor layer comprising at least one Group III element and nitrogen, the method comprising steps of: depositing, on a substrate, a single-crystal Group III nitride compound semiconductor layer comprising at least one Group III element and nitrogen; and removing a lattice defect which occurs in the single-crystal Group III nitride compound semiconductor layer, by irradiating the single-crystal Group III nitride compound semiconductor layer deposited on the substrate with a pulsed laser.
A semiconductor device according to the invention is a semiconductor device comprising a Group III nitride compound semiconductor layer comprising at least one Group III element and nitrogen, wherein the Group III nitride compound semiconductor layer is deposited by sputtering using a target comprised of a Group III nitride compound in a plasma atmosphere of gas comprising at least nitrogen, and has a poly-crystalline structure.
In a deposition method of a Group III nitride compound semiconductor thin film according to the invention, a poly-crystalline Group III nitride compound semiconductor thin film is deposited by sputtering using a Group III nitride compound target in a plasma atmosphere of gas comprising at least nitrogen. Thus, a Group III nitride compound semiconductor thin film of the invention is obtained.
In another deposition method of a Group III nitride compound semiconductor thin film according to the invention, a poly-crystalline Group III nitride compound semiconductor thin film is deposited, and then the poly-crystalline Group III nitride compound semiconductor thin film is irradiated with a pulsed laser.
In still another deposition method of a Group III nitride compound semiconductor thin film according to the invention, a single-crystal Group III nitride compound semiconductor thin film is deposited, and then the single-crystal Group III nitride compound semiconductor thin film is irradiated with a pulsed laser.
In a manufacturing method of a semiconductor device according to the invention, a poly-crystalline Group III nitride compound semiconductor layer is deposited by the deposition method of a Group III nitride compound semiconductor thin film. Thus, a semiconductor device of the invention is obtained.
In another manufacturing method of a semiconductor device according to the invention, a poly-crystalline Group III nitride compound semiconductor layer is deposited by, for example, sputtering, and then the poly-crystalline Group III nitride compound semiconductor layer is irradiated with a pulsed laser.
In still another manufacturing method of a semiconductor device according to the invention, a single-crystal Group III nitride compound semiconductor layer is deposited by, for example, epitaxial growth, and then the single-crystal Group III nitride compound semiconductor layer is irradiated with a pulsed laser.
Other and further objects, features and advantages of the invention will appear more fully from the following description.